The invention relates to forming shoes in a stationary dewatering element for a paper making machine and more particularly to forming shoes within a twin wire former thereof, and to forming shoes which are applicable to the blade of a deflector, the cover plate of a wet box, a suction box, etc.
In one prior arrangement of forming shoes which have previously been used in an upright type twin wire former, raw material supplied from a head box is guided into a narrow path formed by a No. 2 wire and a No. 1 wire. In this instance, the No. 2 wire is supported by forming shoes arranged at given spaced intervals.
Along the path of the paper being formed a pressure difference arises between those portions instantaneously supported by the forming shoes and the other portions. This pressure difference causes local flows to occur both in the direction of travel of the wires and in the opposite direction; these local flows improve the sheet formation and quality of the paper being formed by means of such twin-wire former. On the other hand, however, in the event that this pressure difference becomes too great, short-comings arise in that the retention rate is lowered and the machine-direction to cross-machine-direction ratio becomes large, because the fibres are liable to align themselves in the direction of travel of the wires. It is to be noted that, in these devices the contact surfaces of the shoes with the wire is smooth.